The present invention relates to tracked vehicles for agricultural and construction vehicles and the like, more particularly a pneumatic tire wheel assembly for such tracked vehicles. The wheel assembly having a unique rim assembly for dual wheel mounting.
The use of pneumatic tires on agricultural and construction vehicles dominates the agricultural industry as it is known today. Nevertheless, there is an increasing use of track vehicles for agricultural and construction use. These track vehicles use an endless belt, preferably made of elastomeric material reinforced by cords of steel. The belt has a ground engaging tread surface similar to that found on a tire. The primary benefit to a track system is clearly the increase flotation tracks have over tires. Tracks can bridge a longer surface area, helping to keep the vehicle afloat. In many agricultural and construction applications the use of tracked vehicles is becoming ever increasingly more popular.
In a prior art patent, U.S. Pat. No. 5,279,378 to Charles E. Grawey, et al. a frictionally driven belted work vehicle is disclosed. In that application Grawey discloses the use of a metal-coated wheel assembly having a pair of rigid wheels with a rubber coating as a drive wheel. Also a cushion wheel can be used as a drive wheel and in an alternative embodiment a bias belted pneumatic tire is used in pairs to provide a drive wheel for the belted vehicle. In that application, Grawey et al. advises that the metal or cushioned wheels are preferred over the pneumatic wheels for a variety of reasons. Grawey notes that panagraphing and relative motion between the drive wheel and the belt can not be tolerated and still provide reasonable wear. He further notes that other than the well-known panagraphing which all bias tires experience, bias tires when under load also exhibit a tracing out of the footprint for one revolution thereof which is shorter by approximately 2 or 3% than the circumference around such tires outer periphery when unloaded. Such circumferential changing phenomena causes relative motion between the belt interior surface and the drive wheel tread portions. Such motion results in wear of the leading edge of the tread lugs and, thus, reduces the tractive length of their drive portions. The practical effect of such wearing substantially reduces the wiping action of the tread lugs upon the surface of the belt which in turn reduces the friction coupling between the drive wheel structure and the belt when they are operated in mud or other adverse friction coefficient reducing requirements. Such relative bias wheel to belt movement carrying frictional engagement results in wear of the belt and the tire. The inventor then goes on to note that the lack of relative movement between the track or belt and a cushioned or rigid wheel structure greatly reduces these wear problems.
While the rigid wheels and semi-cushioned or cushioned wheels dramatically reduce the wear problems it is well-known that the vehicle suspension system must be greatly enhanced in order to provide any ride comfort. This dramatically increases the cost of the vehicle and overall the cost of operating a track vehicle system.
It is an object to the present invention to provide a pneumatic wheel assembly that does not exhibit detrimental mud and snow packing characteristics.
It is a further object of the invention that the pneumatic wheel assembly can be used which can accommodate debris and wet soil conditions while still maintain frictional engagement with the belt itself so that forward or reverse propulsion of the vehicle is not dramatically reduced due to a wet or muddy soil condition.
It is a further object of the invention to provide a dual tire rim assembly in both the drive wheel position and the free rolling axle position that avoids the potential for the track to become dislodged due to mud or debris packing.
A dual pneumatic tire rim assembly has a pair of annular rims for mounting a pair of pneumatic tires onto a tracked vehicle.
The rim assembly has a plurality of laterally extending spokes separating each annular rim by a fixed distance. Each spoke is attached to each rim. A central disk extends radially inwardly and is located between the pair of annular rims. The central disk is attached to each spoke and is located at a fixed distance O, O being the amount of offset between the vehicle axle to which the rim assembly is mounted as measured from the centerline (CL) established by the distance halfway between the pair of annular rims.
The preferred embodiment rim assembly is preferably used on tracked vehicles employing pneumatic tires in the drive wheel position and the free floating axle position, or, as in the case of skid steer equipment, an all drive wheel vehicle. (Notexe2x80x94skid steer vehicles have the front and rear axles on each side connected by a chain from a central drive axle. The left and right sides are independent.)